1. Field of the Invention
The present invention relates to a technique for controlling a data size of an electronic mail.
2. Description of the Background Art
There has been known an electronic mail software program which operates on a terminal such as personal computer. An electronic mail that a sender sent using electronic mail software is transferred to a mail server of sender side specified in the electronic mail software. The mail server sends the received electronic mail to a mail server of recipient side where a post of a destination electronic mail address exists, in accordance with the destination electronic mail address. Likewise, the recipient receives the electronic mail that has been mailed in his/her own post with the use of electronic mail software operating on a terminal such as personal computer. In this way, the electronic mail system is operated.
In the above system, an electronic mail sent by a sender is transferred by a mail server of sender side. However, since a mail server serves to process electronic mails of a number of users, it provides a limitation for a data size of electronic mail from the view of its throughput or servability.
In view of this, Japanese Patent Application Laid-Open No. 2000-29797 and Japanese Patent Application Laid-Open 2001-14235 disclose techniques in which electronic mail software downloads from a mail server of sender side information regarding a limitation of data size, and cancels sending of electronic mails of data size larger than the limitation.
Furthermore, Japanese Patent Application Laid-Open No. 11-196218(1999) discloses a technique in which an electronic mail having a data size of equal to or more than a specified data size is sent by being divided. Also, Japanese Patent Application Laid-Open No. 11-32196(1999) discloses a technique in which information of data size which is specified for every network type is possessed and a data size of a send mail is limited.
In this way, such a case that a sent electronic mail is rejected by a mail server and sent back as an error mail is avoided.
However, in the techniques disclosed in the above described Japanese Patent Application Laid-Open No. 2000-29797 and Japanese Patent Application Laid-Open No. 2001-14235, only the data size limited by the mail server of sender side is take into consideration, so that if the sent mail is having a size that exceeds a limitation of data size provided by a mail server of recipient side or a relay mail server passed by in transmission path between the mail server of sender side and the mail server of recipient side, the mail will be sent back as an error mail.
In addition, the technique disclosed in Japanese Patent Application Laid-Open No. 11-196218(1999) is premised on the fact that limitation values of data size specified for individual mail servers can be acquired, while the technique disclosed in Japanese Patent Application Laid-Open No. 11-32196(1999) is premised on that limitation values of data size specified for individual network types can be acquired. For this reason, these technique are not applicable when firm limitation values specified for individual mail servers and networks cannot be acquired, and still have a problem that an electronic mail having a relatively large data size is sent back as an error mail.